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Paratuberculosis in cattle places heavy financial burden on agriculture. However, it can be combated far more cheaply using a smarter testing strategy.

By Carsten Kirkeby

Each year in Denmark, many cows contract the disease paratuberculosis which is caused by a bacterial infection. The infected animals display a range of symptoms, including reduced milk yield and severe diarrhoea—and the disease may eventually lead to the death of the animal.

But now, using a computer model, researchers from DTU and the University of Copenhagen have simulated several different strategies to combat the disease, showing that the agriculture sector can combat paratuberculosis far more cheaply by using smarter testing methods.

When a herd becomes infected with paratuberculosis, the affected animals can infect other animals long before symptoms appear, and detecting infected animals before the final stages of the disease is difficult—making it hard to treat. The bacteria can survive for a long time in the cowshed and many farmers simply throw in the towel, even though the disease may end up costing them dearly.

Using a computer model, researchers from DTU and the University of Copenhagen have developed strategies that simulate every facet of a Danish dairy herd. In all the simulated strategies, animals that were tested positive were slaughtered.

The simulations show that if herds are tested more frequently when there is a high incidence of infection, farmers can save a lot of money while at the same time combating paratuberculosis. In other words, the disease can be combated using the same approach and with the same results—but less expensively if farmers adopt smarter testing methods.

Expensive testing
Paratuberculosis is common in Danish dairy herds. Up to 70 per cent of the country’s herds are infected with the disease caused by the bacterium Mycobacterium avium subspecies paratuberculosis.
Denmark has a voluntary control programme—Operation Paratuberculosis—which is helping farmers to fight the disease. Approximately 25 per cent of Danish farmers subscribe to Operation Paratuberculosis and pay to have their cows tested quarterly.

Each test costs approximately EUR 5 (DKK 40), and this quickly adds up when you consider that an average herd numbers around 180 dairy cows.

Understandably, many farmers are reluctant to participate, especially those with large herds and therefore high testing costs. But even farmers with only a few infected animals may feel that it is too expensive to test entire herds when only a few of their cows are ill. This is a problem because if farmers do not test their herds or take other precautionary measures against paratuberculosis, the number of infected animals can easily increase.

This gave the research group the idea of developing a flexible test programme. The idea is for herds with a high incidence of infection to be frequently tested and infected animals slaughtered in order to limit the number of paratuberculosis cases.

The same result—but cheaper
After a few years—when there are very few infected animals in the herd—testing can be carried out less frequently. This allows the farmer to save money while still making a targeted effort to eliminate the disease.

Before the research group had simulated the results, they had no way of knowing whether less frequent testing would be enough to combat the disease. However, their results showed that it is possible to keep the disease in check using the flexible approach. In some cases, paratuberculosis could even be eliminated from the herd.

By using the new flexible test strategy in conjunction with the existing system, the research group calculated that a farmer with approximately 200 cows can save almost EUR 540 (DKK 4,000) a year using the flexible approach—as opposed to testing all his cows on a quarterly basis.

Technical University of Denmark

Founded in 1829 with the mission of creating value for the benefit of society, DTU is an international elite technical university where education, scientific advice, and innovation rest on a solid foundation of world-class research.

The University is at the academic and multidisciplinary forefront of the technical and the natural sciences—with new initiatives in a number of demanding engineering disciplines, including sustainable energy technology and life science.